The fundamental principle of ultrasound imaging is to use acoustic waves to help image an object. The basic blocks for ultrasound imaging is the use of an array 10 of piezoelectric transducers (T) in which each transducer will require a high voltage transmitter block (TX), a transmit/receive switch block (T/R Switch), and a low noise receiver block (RX) as shown in FIG. 1.
In each transducer (T), the transmitter (TX) sends out a ±100V 5.0 MHz pulse into the piezoelectric transducer (PZT). At the same time, the transmit/receive switch (T/R Switch) is protecting the receiver (RX) against the ±100V signal. The transmit signal causes the piezoelectric transducer (PZT) to vibrate thereby creating an acoustic wave. The acoustic wave hits the object to be imaged 12. An acoustic echo is bounced back into the transducer (T). The transducer (T) now converts the acoustic echo into an electric signal, which can be referred to as the receive signal, is normally no greater than a few 100 millivolts. The transmit/receive switch (T/R Switch) allows the small receive signal to pass into the receiver (RX). The signal from the receiver (RX) is used to help reconstruct a small part of the image. The remaining channels are used in a similar fashion to help reconstruct a complete image of the object.
The transmit/receive switch (T/R Switch) is commonly implemented using high voltage diodes, D1, D2, D3, and D4 configured as a diode bridge and a means of biasing the diodes. This is shown in FIG. 2.
The T/R Switch must have a very fast response time in order to effectively protect the receiver (RX). This is because the transmit signal is very high in frequency and voltage. During the receive mode, the T/R Switch must not introduce any noise, distort or attenuate the receive signal going into the receiver (RX). The ±5.0V supplies along with R2 and R3 sets the bias currents for D1, D2, D3, and D4. Electrical noise on the +5.0V supply is filtered by R1 and C1 and blocked by L1. Electrical noise on the −5.0V supply is filtered by R4 and C2 and blocked by L2. L1 and L2 are also used to keep C1 and C2 from attenuating the receive signal. There is a total of 12 components for every T/R Switch.
The diodes D1, D2, D3, and D4 are constantly being biased. For a system having 128 channels or even more will create a power consumption concern. The component count also creates problems for the printed circuit board layout as it consume a lot of area and must be strategically placed to minimize electric noise. The ±5.0V power lines must be routed to all the channels which in itself are a nuisance due to the large channel count. As the demand for more channels increases, the need for an improved T/R switch is warranted.
Therefore, a need existed to provide a system and method to overcome the above problems. The system and method will provide a more compact TR switch. It should be noted that while the above Background discloses an ultrasound application, the present invention is not limited to ultrasound application. The present invention disclosed below may be used in other applications such as but not limited to: a resettable fuse, data acquisition input protection, and output short circuit protection.